In the physical simulation experiment related to the oil-gas reservoir exploitation, the pressure of the simulated oil-gas reservoir may be up to more than 30 MPa, while the minimum differential pressure for the simulation experiment of the seepage and oil-displacement which needs to be measured may be less than 0.01 MPa.
The conventional differential pressure gauge cannot accurately measure a micro differential pressure under a high pressure condition of several tens of MPa, and hence cannot accurately measure a dynamic change or fluctuation of the micro differential pressure during the experiment. The principle of the piezoelectric differential pressure transducer is to sense a pressure through a pressure-measuring diaphragm, with the thickened pressure-measuring diaphragm leading to a low measurement accuracy (the deviation is 0.24 MPa) when being used under a high pressure condition (40 MPa). The compensative micro differential pressure gauge is based on the pressure-measuring principle of the U-tube manometer, and its usage pressure range is from 0 MPa to 2.5×10−3 MPa due to the pressure tolerance limitation of the glass tube. The capacitive micro differential pressure gauge measures a differential pressure by measuring a capacitance variation caused by the differential pressure, and it cannot measure a micro differential pressure under a high pressure condition. The Chinese patent application No. 201510178391.0 discloses a micro differential pressure gauging device for high pressure experiment, which automatically searches a liquid level variation through optical grating, thereby achieving a micro differential pressure measurement under a high pressure condition, with the liquid level identification accuracy reaching 0.1 mm. But the automatic searching by the optical grating takes a long time, and the measurement cannot be completed until the differential pressure becomes steady, thus the continuous gauging of a dynamic micro differential pressure varying with time cannot be realized.
Therefore, the dynamic gauging of a dynamic micro differential pressure for a high pressure experiment is the technical difficulty urgently needs to be solved for experiments related to the oil-gas reservoir (in particular tight oil-gas reservoir) exploration.